Abscisic Acid Modulates Physiological and Proteomic Changes During Histodifferentiation and Germination of Somatic Embryos in Euterpe edulis

Abstract Euterpe edulis Martius (juçara palm) is an endangered species of high ecological and economic importance. Its propagation via reproduction is limited by the recalcitrance of its seeds, which hinders conservation and genetic improvement. Somatic embryogenesis represents an efficient alternative for large-scale clonal propagation and conservation. The present study evaluated the effect of abscisic acid (ABA) on histodifferentiation and germination of somatic embryos, to optimize in vitro regeneration of E. edulis . High rates of histodifferentiation (~ 98%) and germination (~ 95%) were achieved with 5 µM ABA, resulting in vigorous embryos with well-developed haustoria. Higher ABA concentrations (10–15 µM) were associated with reduced germination and delayed developmental progression, whereas the absence of ABA impaired histodifferentiation and embryo vigor. Proteomic profiling revealed increased accumulation of structural proteins (β-TUB7, TUBB1, TUBB5), chaperones (HSP83), proteasome components (PSMA2-like), energy metabolism enzymes (GAPDH2, PFK, PFP-α), tricarboxylic acid/glyoxysomal enzymes (SDH5, MDH-glyox), and nitrogen/methylation enzymes (GS, AHCY) in embryos treated with 5 µM ABA, suggesting associations with cytoskeletal remodeling, mitochondrial stability, epigenetic adjustments, and selective translation. In contrast, a decrease in defense proteins such as PR1 reflected a typical developmental trade-off. ABA also involves the integration of hormonal adjustments and the regulation of antioxidant enzymes. In summary, 5 µM ABA promotes efficient histodifferentiation and germination of embryos, enabling in vitro cloning, conservation, and genetic improvement of the species.